Door knob lock monitoring alarm mechanism

Abstract

An interior door knob for conventional lockable door latches includes a hollow knob with a cylindrical neck having conventional means for engaging and rotating the latch spindle to mechanically move the door bolt and an actuator mechanically engaging the locking mechanism of the door latch and extending through the cylindrical neck into the housing and being movable between a first and a second position. A battery, an acoustic/visual indicating means and a normally-open microswitch electrically connected in series are mounted in a component module received within the knob housing. The microswitch switches responsive to the position of the actuator for indicating when the locking mechanism of the door latch is not locked.

We claim: 
     
       1. In a lockable door latch having turnable exterior and interior knobs for mechanically rotating a spindle for moving a door bolt in and out of engagement with a strike plate mounted in a door jamb, and having a manually operated interior mechanism for locking and releasing a locking mechanism, an interior knob incorporating a lock monitoring alarm comprising in combination, a knob housing having a cylindrical receptacle and an integral cylindrical neck coaxially extending therefrom, the cylindrical neck including means for engaging and mechanically rotating the spindle when the knob housing is turned,   an actuator member extending from within the knob housing, through the cylindrical neck of the knob housing for mechanically engaging the locking mechanism, the actuator member being mechanically moved between a lock position and an unlock position as the locking mechanism engages and disengages respectively,   a source of electrical energy located within the knob housing having at least a pair of terminals, each electrically insulated from the other,   a normally-open electrical switching means located within the knob housing and mechanically coupled to the actuator member for opening and closing responsive to the lock and unlock positions of the actuator member, respectively,   an electrically energized indicator means located within the knob housing for generating a signal perceptible to a human being upon being energized with electrical energy,   electrical current conductor means for electrically connecting the switching means and the indicator means in series between the terminals of the electrical energy source, whereby the indicator means is energized when the switching means is closed.   
     
     
       2. The door knob of claim 1 and further including a removable circular cap member having a closure surface for closing the cylindrical receptacle of the knob housing. 
     
     
       3. The door knob of claim 2 wherein the locking mechanism of the door latch is engaged and disengaged by rotating the actuator member, and   the actuator member comprises a rod with an end extending through the removable cap, and further including,   a thumb-finger graspable knob secured to the extending end of the actuator member, whereby the actuator member can be manually rotated for engaging and disengaging the locking mechanism, and wherein   the actuator member has a first camming surface and a second camming surface oriented in rotational sequence around the actuator rod, the first camming surface having a greater radial height than the second camming surface, and wherein   the normally-open electrical switching includes cam following means engaging and following the cam surfaces of the actuator as the actuator rotates between the lock position corresponding to the first camming surface for mechanically closing the switch and the unlock position corresponding to the second camming surface for mechanically opening the switch.   
     
     
       4. The door knob of claim 1 wherein the electrically energized indicator means comprises a buzzer for generating an audio output of at least 70 db at a frequency perceptible by human beings. 
     
     
       5. The door knob of claim 1 wherein the electrically energized indicator means comprises a light emitting diode having an optical emission perceptible by human beings. 
     
     
       6. The door knob of claim 2 wherein the electrically energized indicator means comprises a buzzer for generating an audio output of at least 70 db at a frequency perceptible by human beings and a light emitting diode having an optical emission perceptible by human beings, and wherein the removable circular cap member includes an audio grill port and an optical port communicating through its closure surface. 
     
     
       7. The door knob of claim 1 wherein the locking mechanism of the door latch is engaged and disengaged by a yoke mechanism translating perpendicularly relative to an axis coaxial with the spindle, and wherein the actuator member comprises a toggle rod mechanically coupled at one end to the yoke mechanism, its remaining and extending into the receptacle of the knob housing, and further including, a cylindrical sleeve received within the neck of the knob housing,   a pivot pin located diametrically across the cylindrical sleeve securing the toggle rod whereby translation of the yoke mechanism between its engaged and disengaged positions pivots the remaining end of the rod within the receptacle of the knob housing between the lock and the unlock positions, respectively, and wherein,   the normally-open electrical switching means includes a spring return sensor button mechanism for establishing an electrical connection when depressed mounted and positioned within the receptacle of the knob housing such that its sensor button is depressed by the remaining end of the rod when it is at the unlock position.   
     
     
       8. An interior door knob incorporating a lock monitoring alarm comprising in combination, an interior knob housing having a cylindrical receptacle and an integral cylindrical neck coaxially extending therefrom, the cylindrical neck including means for engaging and mechanically rotating a spindle opening a lockable door latch when the knob housing is turned,   an actuator member extending from within the knob housing, through the cylindrical neck of the knob housing and mechanically coupled to a locking mechanism within the lockable door latch for preventing rotation of the spindle by an interior knob, the actuator member being mechanically moved between a lock position and an unlock position as the locking mechanism engages and disengages respectively,   a source of electrical energy located within the interior knob housing having at least a pair of terminals, each electrically insulated from the other, a normally-open electrical switching means located within the interior knob housing and mechanically coupled to the actuator member for opening and closing said switching means responsive to the lock and unlock positions of the actuator member, respectively,   electrically energized indicator means located within the interior knob housing for generating an audio output of at least 70 db at a frequency perceptible by human beings and for generating a light emission perceptible by human beings upon being energized with electrical energy,   electrical current conducting means for electrically connecting the switching means and the indicator means in series between the terminals of the electrical energy source, whereby the indicator means is energized when the switching means is closed,     a removable circular cap member closing the cylindrical receptacle of the knob housing and having an audio grill port and an optical port communicating through its closure surface.   
     
     
       9. The interior door knob of claim 6 or 8 further including a cylindrical component module having a central passageway, and wherein the normally-open electrical switching means, the source of electrical energy, the electrically energized indicator means and the electrical current conducting means are each secured and positioned within the module, the module being interchangeably receivable in the receptacles of a plurality of different interior knob housings.